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Tuesday, February 19, 2013

Yea so I did a CAD thing with a lot of procrastinating along the way.
Concluding thoughts: sleep. Also do more schoolwork / UA work and also apply to jobs. Good plan.
Oh, include more margin of error in general, in this case for the diameter of the can with cat5 cable included (you can see where I bandsawed the top platform just to see how it would do).

redo by making platform higher

oh and fix the snap fits

and make things a bit farther apart

Acrylic, it snaps.

the video is actually made still using this piece. actually maybe the extra degrees of freedom allow the vehicle to actually work.

Monday, February 18, 2013

lately i've taken to the "make rough sketch of parts on paper, then in solidworks, make solidworks assembly, then add all the features at the correct location with the help of CAD" method of making things. With the lasercutter especially, something you want is that if you decide to change your stock (or you measure incorrectly), you can change the thickness of your features all at once.

This puzzled me a while back, because if you try to enter an "equals" sign into the extrude feature to create a variable like you would when dimensioning a sketch, you get an error:

error to the left

Uh, so...? What? You can't use equations in features? That's dumb.

Thankfully that's not the case. Turns out you input whatever for the feature and click the check mark. Then you go back and double-click on that feature (in this case boss-extrude) in the feature tree,

which pops up the "extrude" feature dimension on your model,

which you can then double-click to edit. And insert an "=" sign to create a variable.

Okay, so that's great. But this variable only exists within this one file. How do I get it into other files?

There's the "material_thickness" variable I created as = 12.5, and then there's the "first extrude = material_thickness" which is sort of optional for exporting. All my features are meant for lasercutting so I may as well export the fact that the first extrude-boss should be of "material_thickness" thickness.

(That is, when I import in the future, I have to make sure the new file has an extrude already, or else the "equation is invalid" error will pop up because it's like "wtf there is no extrude thickness dimension to link to in this file". So probably best actually not to export that extrude thickness dimension, or else un-check that equation when importing).

This saves it as equations.txt

Then I create a new part (for demo purposes) and import the equations file:

And voila, everything has carried over.

NOTE: Watch your units! As you can see, the equations file doesn't have units. So if you export as 12.5 mm in one document and then import in a document that is set to work in inches, you get a 12.5 in part.

If I want to edit the variable, I have to do so externally. At the bottom of Tools > Equations, there's an "open file" button that I use and it pops open the equations.txt file in the default text editor (in this case notepad)

i have been making a lot of things lately.
Never enough!
But yes, I rediscovered the lasercutter, and there happens to be one upstairs of MITERS now.*

* [I should really get a Real Laptop (that I can CAD on) and then I have no excuse to hang around upstairs when the MITERS computers are occupied. (or just set up another computer downstairs...) but in the meantime there are excellent computers are the third floor (which as a bonus are tucked away in corners. I have a special affinity for corners).]

So he made his prototype out of PVC pipe. Specifically, giant!diameter!PVC pipe for the augur and 1/4'' diameter pipe wound around the large pipe for the threads on the augur. His second revision was tube aluminum with specialty-ordered sheet steel threads (the two were held together with "Loctite E-20NS metal epoxy". Wow. Heavy-duty epoxy).

Well! I wanted to complete snow-bot in a day so I decided to make it out of coke can + cat 5 cable hotglued onto it (with revision two to be 3d printed).

that is so totally a workable augur. right?

This err didn't happen. I got distracted by other lasercut projects. But yea, the plan was to attach two continuous rotation servos to turn the coke cans and voila, I would have instant prototype.

note: for the sake of sleep this is going to be an overview post with more detailed / better formatted / all my files--posts to come, but in case I don't get around to those:

My first step was to discover that I had SpringerRC continuous rotation servos, perfect for the job, but no servo horns. (First of all, note that servo horns are NOT all compatible). Oh noes! Well. Turns out, they are pretty easy to make, despite the total lack of help from this site which just says "lol they are easy to make":

A bit of googling and double-checking by counting by hand, I find out futaba-compatible horns have 25 "teeth." And using calipers I determine the outer and estimate the inner diameter, for which I get roughly 0.02'' which order-of-magnitude agrees with the super-accurate measurements made by this dude.

I also, via the internet (and later by trial-and-error) find 3mm acrylic-like plastic to have a kerf of about 0.005''.

So using coreldraw (or inkscape), there is a polygon/star tool, and I enter 25 pointed star. I then eye-ball the "sharpness" parameter, which you have a bit of slack on (the horn teeth just needs to fit between the servo teeth). I also initially set the x-y width to be 0.235'', the exact outer-diameter I measured. When cut out, this servo horn a bit loose but slides onto the servo and turns the servo when it is turned.

yes. my camera has a permanent dust speck somewhere inside it...

Then I iterate. You can see I drew a green and yellow rectangle, for 0.02'' + 0.005'' kerf, to get the "sharpness" (pointiness of the star) setting right (if you draw it out, to account for kerf, the OD of the star should be smaller by 1/2 kerf and possibly the star's inner corners should go 1/2 kerf deeper, hence why 16 sharpness with the inner corner somewhere between the length of the green and yellow rectangles. I'm not 100% how sharpness is interconnected with the diameter of the star so it's hard to say what the exact adjustment should be).

f* yea MS Paint

The laser settings I used for a 120W epilog laser:

Of course, I don't finish over the weekend and Monday I walk into 2.007 lab (which I am undergrad assisting with, UAing, this term) and there are a gazillion springerRC servos and servo horns. But that's beside the point.

I also realized that part of my search criteria for LIFE aka a career included "access to lasercutter," but maybe I am supposed to look for a job that pays well so that I can buy my own lasercutter. Hrm.

Hrm...

Anyway, what else happened? Oh right, Jordan's birthday came up. Because she is awesome, I decided I should make her a birthday gift. Inspired by Kat Struckmann's cruftmas (putz hall secret santa tradition where gift has to be entirely made of cruft, aka free stuff. Oh right, I made a sheet steel bookstand for my secret santa and learned the importance of product design, because the gal I gave it to was like "wtf is this, a shelf?" ^^; #toblogabout) gift to Sterling Harper, aka by the Archer TV show:

image courtesy of jordan.

Oh gosh. I had to use so many programs to make this, I don't even. No. Anyway, the general idea is to use various selection tools (oh robutts don't use the polygon tool by itself, it's so easy to accidentally hit escape and erase all your work with the selection, make sure to use quick-mask model with shift-Q -- everything this is orange is not in the selection and everything that is white is) in GIMP on the original image (see: her blog), export selection to path, save path as an SVG, import that into inkscape, use various path tools (difference, something like that) to merge the Person outline with the rectangle outline that I want to cut out to create a stencil-like effect, realize that coreldraw hates inkscape SVGs for whatever reason, save inkscape file as PDF and import and clean up import in coreldraw, still recreate a lot of the work in coreldraw because I am more familiar with sending coreldraw files to the lasercutter, find flowers on openclipart, and then spend a few hours playing around with the DPI / whatever settings because I want to get a raster image of the photograph etched onto the outline. This... doesn't go so well. Somewhere along the way I decide to add a ruler to the thing, because really, useless keychains may as well have rulers on them. I discover the magical coreldraw "blend" tool, where I can just draw two lines at the beginning and end and then specify how many copies I want to use to blend between them (since the end and beginning lines are the same, all the intermediates are the same as well).

so many rejects. luckily this is all from small bits of scrap other people would probably just throw right out.

Then there were other lasercutter shenanigans, but that's for another time. Briefly...

Oh gosh that is a topic in and of itself. Inkscape has a gear generator, but then I tried to x-y scale that, so the pitch becomes something strange, and then I import that dxf into solidworks to make a 3d model and also to measure the pitch and other things, and later export it as a dxf from solidworks to coreldraw ... ... apparently solidworks has a gear generator in its toolbox. I should use that next time.

Hrm this is rich with possibilities. I CAN EMBED SO MUCH ELECTRONICS IN HERE with this 3d possibility.

Heck I could like embed a mini hexapod in there probably. With a button. So I can hit the button and pop out a small hexapod army from brace/ankle-lets.

HRM.

Hexapod armies.

*reminds self to talk about microcenter and finding hexy, the kickstarter project funded just seven months ago, on the shelves there....* #toblogabout

Okay, when my blog posts get to the topic of hexapod armies it's a definite sign that I am procrastinating. Time to get back to CADing snowbot. (CADing a spontaneous robot? wtf? MIT, what have you done to me, that I would prefer to CAD and lasercut something instead of putting things together by hand until it works...)

Wednesday, February 13, 2013

I made a video about hexapods! yay. I'd estimate it was a full 4 or 5 days working on it, learning final cut pro along the way. It basically covers my journey through 2.007 two years ago, and is meant to be a resource for students in the class.

Note to self: shortcuts: < > ctrl-= alt-w

Meanwhile, I think an instructable a week sounds like an excellent plan for Spring semester senior year.

Saturday, February 9, 2013

So, I didn't get into 2.72 build-a-lathe-you-can-sledgehammer-on class, which my brain had decided was my last salvation at actually believing I qualify for graduating as a mechanical engineer from MIT in June. I guess I'm just doomed to make shoddily put together things until I get real life experience or something. I guess the example that comes to mind is makerbot v1, but there's also something to be said for getting something out the door instead of being worried about whether it is Acceptable.

It's also supposed to snow a lot so school was canceled for today, so I decided to sulk by coding all day. Bletch, take that course 2. Or something. XD; There's a course, 6.170 (no, not your grandmother's 6.170, which was toned down into today's 6.005; this is now software development principles through the view of web app dev apparently) which I might follow along with. It's taught in ruby this year, but it was taught in flask last year so there's some nice material on stellar. http://stellar.mit.edu/S/course/6/sp12/6.170/materials.html

instead of

from flaskext.login import LoginManager

resetting from zip file

Mm. At this point, I just downloaded the microblog-0.5 zip file, unzipped, did the whole virtualenv / pip install flask ordeal, ran ./db_create.py and ./db_migrate.py, and everything is now dandy.part VI.

I didn't have an image for my email address (well, I'd used plus addressing when signing up for Gravatar but not when signing into the google openID thing, and I didn't feel like restarting my browser to disassociate myself from the google openID thing). The gravatar took a few seconds to update. To check the code was working, I used

This spits out
'http://www.gravatar.com/avatar/79424cef70fbb561ff50512c2c03334f?d=mm&s'
which worked just fine in the browser, and upon refreshing the app, showed up in the app as well instead of the mystery-man human outline icon.

Well. Now I know why all those silly web-apps make me sign up for gravatar instead of letting me upload pictures. Because it's easier to use someone else's service...

part vii

http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-vii-unit-testing
I was kind of confused by this part (he explains in more detail later), but keeping the None values works and you can enter whatever into the email address for the admins list.

*blinks* I'm still a bit confused, since I followed the instructions instead of just using the install script. Not actually being course 6, I'm not sure which parts of my ~/.vimrc folder I should put up on a git server (github). *shrug* I can always recreate it now. (I lost my dotfiles after google summer of code '11 and missed them for a while). https://github.com/nouyang/dotfiles

Yuck. Ignore previous paragraph. I can't get the leader key to work. (What is that leader thing? Turns outmaps to \ by default.)

The symptoms look like this. also relevant, following this gal's example I just reinstall everything.
So, I end up removing my entire .vim folder and reinstall with the sontek install script. Which requires I install ruby first... Whoops, it says rake: command not found.

NOTE:If you are in paste mode, the "jj " mapping will not work.
Also, if you set mouse mode on, you can't copy-paste out of the
terminal. And if you set line numbers on, when you copy-paste the line
numbers get copy-pasted too. And on gnome-terminal (or ubuntu?) F10
seems to map to pulling down the toolbar options, so I used F12 instead.
I also changed this tab-spaces = 4 instead of 3, because python.

So now, some of the shortcuts I can use:
:e to open a buffer, and ctrl-6 or :b1 to go to whichever buffer is open.
>> and << for indenting to turn on/off paste mode
:x to save and close (NOTE! I have, as mentioned, mapped ; to :)
:nmap to look at my shortcuts

resetting .bashrc for ubuntu, not mac

Meh, as usual with the internet, the .bashrc on sontek's site is for mac osx and not ubuntu. I wanted to color my prompt, so I reverted to the default .bashrchttps://gist.github.com/marioBonales/1637696
Note that thanks to using the install script, I have a bunch of symlinks and the file I actually want to edit is ~/dotfiles/_bashrc ...

back to flask / jinja

lol. that took forever and a few inches of snow. It's now... 1900. and snow's supposed to get heavy around 9pm. Okay! Time to get going.

==/note to self: productive = keep door open and headphones in. otherwise,
i feel jittery with the door open for some reason, I close it, and then
I fall asleep in an unmotivated heap. =__=;; derp hopefully this too will pass with time. also, being productive feels nice, no matter what particular item i choose to finish on #infiniteprojectlist.Also, an interesting way to keep track of time passing (usually I use onlinevideoclock.com or tomatoi.st), set my netbook to go to sleep every 30 minutes and use it to play music while working on my desktop.

If you want to add a long list of names to a list, you can put them all in a text file and do 'blanche listname -al filename', or if you want a list to contain only the names in a text file, you can type 'blanche listname -f filename' and the appropriate members will be both added and removed

Thus, at a terminal, I would go

narw@ubuntu:~$ ssh nouyang@linux.mit.edu [remote login to athena]
nouyang@dr-wily:~$ vi 2.007ua [make a file with a list of athena usernames. it will accept the @mit.edu but it's happier without. You can do this with gedit if you want.]
nouyang@dr-wily:~$ blanche 2.007-2013uas -al 2.007ua
voila! done. If you want to double-check they've been added, just do

Sunday, February 3, 2013

This past week I finally got started on my crazy half-formed ideas about an MITx version of 2.007.

Things I learned:

use camstudio for screencasting on windows (free). Note that past 2gb, or less than 3 minutes using the Intel format at 50 quality (see screenshot later in post), the avi files seem to get corrupted and unusable.I'd looked into using ezvid, but you can only export to youtube.

record in a nice place, not a stone dungeon, because it reflects in the audio

macs don't like windows-formatted hard drives, so you can read but not write from non-mac-specific external hard drives

MIT specific: the "scratch" folder on the building 26 new media / macathena clusters is per-computer, so you have to log-in at the same computer to access those files. I panicked when fcpx froze and I logged in on another computer and didn't see anything in the scratch folder...

on linux, youtube-dl blahlink will download the highest resolution version of blahlink video

fcpx does not like flv files, and likes wav rather than mp3 files (if your recorder gives you that option)

hexapods video

(cc zero) made in inkscape + gimp + solidworks screenshot.

OKAY EVERYONE.I'm still alive! I lolfailed at making a comic over IAP, but that is okay. Because! I ramped back up into happy excited mode! I hope this lasts more than 24 hours. I'm stressed about The Future but what the heck I am now able to convince myself to enjoy the moment and not be all "I should have done this by now" and "f***there's a million things I should do, maybe i should just sleep instead."Thanks, brain. *scrunches face* I wonder about saying things like this when I am trying to find a job. oh well!

Anyway, I spent the last few days working on a video about hexapods, ostensibly to help people understand the design process for 2.007. (I made 18-servo-pod for 2.007 instead of participating in the contest). I'd taken part in a documentary-making class before, which used the final cut pro installed on the macs in the New Media Athena Cluster in building 26.

But this was a bit different. For one thing, neither of the two hexapods (linkage and 18 servo) work right now. For another, since it's a video about the design process, basically I am stuck with whatever media I took 2 years ago. So I have a lot less video and more pictures than might be ideal.

Anyway, turns out video editing software (in my case, final cut pro x) is magical and there's no need about worrying about timing my screencasts with my audio recordings (which are done separately -- I probably read each paragraph of the script 3 or 4 times) (The main advantage of reading it paragraph by paragraph is when you make a mistake reading it, you can re-record just that paragraph).

I used a stand-alone mic from a friend, and transferred sd-card files.

Using multiple monitors

My setup was like so:

Note the camstudio video settings, I think way lower would still be fine.. It also used to automatically open the avi file after recording, which got annoying so I turned that off.

I have two monitors, so I set the rightmost one to be 1280x720 resolution, lower than it can be.Camstudio has a "select screen" option so it will only record one screen. Zoomit didn't handle multiple screen as gracefully -- I ended up making my right monitor the default (bringing the taskbar along with it :'( ) because it would let me type, but not draw, if I activated it (hit ctrl-2) on the wrong screen.

final cut pro x

Relatively intuitive to use. I used option-w to insert gaps (for breathers), cmd-r to "retime" edit the length of clips, and to make the end of a video sustained, I did it hackisly by cutting (b for blade) the end of a video and then using cmd-r to stretch that to however long I wanted it. There's also automatic audio enhancements -- I used "background hum removal' a lot, and I need to go back and auto-enhance audio for all of them (I spoke rather softly).

other shortcuts: < and > for moving items around, ctrl-= for increasing 1db audio level, alt-w for insert gap.
oh I also learned -12 dB is a pretty standard audio level (depends on if you expect your video to be on tinny computer speakers or on real audio equipment) and you never want audio to reach 0 dB (when speakers distory).

result

I need to figure out the purpose of this video so that I can add and intro and conclusion to it. Also, credits. I tried to keep most of the reused videos / pictures in-browser so I'm not directly re-using someone's video; I wonder if using 6 seconds of the dancing hexapods video is acceptable? Unclear, but I decided in favor of making something rather than twiddling my thumbs worrying about things.